The Stomach

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Transcript of The Stomach

The StomachWhat is the Stomach?pouch-like organ that hangs inferior to the diaphragm has a capacity of about 1 literreceives food from the esophagus, mixes the food with gastric juice, initiates protein digestion, and moves food into the small intestine Parts of the StomachGastric Secretions3 types of secretory cells:Steps to breaking down food4 Main PartsCardia: small area near esophageal openingFundus: temporary storage unit; balloons superior to the cardiaBody: main part of stomachPylorus: two parts- Pyloric Antrum: bottom of stomach nearing pyloric canalPyloric Canal: narrowing part as it approaches small intestine

2 SphinctersCardiac Sphincter: smooth muscles where the esophagus joins the stomach, allowing food to pass into the stomachPyloric Sphincter: where the stomach joins the small intestine, the muscles allowing food to pass into the small intestineRegulation of Gastric Secretionsgastric juice is produced continuously but the rate varies and is controlled both neurally and hormonally when a person tastes, smells, or sees food, or when food enters the stomach, parasympathetic impulses stimulate release of Acetylcholine (Ach) from nerve endingsAch stimulates gastric glands to secrete abundant gastric juicethese parasympathetic impulses also stimulate certain stomach cells to release peptide hormone Gastrin, which increases activity of gastric glandsas food moves into the small intestine, acid triggers sympathetic nerve impulses that inhibit gastric juice secretionsat the same time, proteins and fats in this region of the intestine cause intestinal wall to release peptide hormone Cholecystokinin (CCK)this hormonal action decreases gastric motility as small intestine fills with foodGastric Absorptiongastric enzymes begin breaking down proteins but stomach wall is not well adapted to absorbing digestive productsstomach absorbs only small volumes of water and certain salts as well as certain lipid-soluble drugsAlcohol, not a nutrient, is absorbed both in the small intestine and stomachMixing and Emptying Actionsfollowing a meal, mixing movements of stomach wall aid in producing semifluid paste of food particles and gastric juice called ChymePeristaltic waves push chyme toward pylorus and as chyme accumulates near pyloric sphincter, this muscle begins to relaxstomach contractions push chyme a little at a time into the small intestinerate at which stomach empties depends on fluidity of chyme and type of food presentas chyme enters duodenum, the pancreas, liver, and gallbladder add their secretionsVomitingvomiting results from a complex reflex that empties stomach in reverse of normal directionirritation or expansion in stomach or intestines can trigger vomitingsensory impulses travel from site of stimulation to vomiting center in Medulla Oblongata, and motor responses followtaking deep breath, raising soft palate, closing opening to trachea, relaxing muscle fibers at base of esophagus, contracting diaphragm downward, contracting abdominal wall musclesas a result, stomach is squeezed from all sides, forcing its contents upward and outUlcersarea of stomach irritated from exposure to gastric juices due to lack of mucus in that areaopen sore in skin or mucous membrane resulting from localized tissue breakdownassociated with stress until around 1982treated with a short course of antibiotics, often combined with acid lowering drugsStomach Cancer (Gastric Cancer)Acid Reflux Fun FactsStomach lining is regenerated about every 2 weekswhen you blush, inside of stomach turns redstarfish can turn its stomach inside outmoths don't have a stomachpeople can live without a stomachPepsi is named after pepsin, the digestive enzyme in the stomachhttp://www.today.com/video/today/49238269#49238269Mucous CellsWhat do they secrete?A viscous, alkaline secretion that coats the inside of the stomach wall; prevents the stomach from digesting itselfWhere are they located?causes about 700,000 deaths worldwide per yearcan be asymptomatic or have no apparent symptomssymptoms can be similar to those of minor illnessesby the time symptoms occur the cancer has already progressed into later stagesin most cases is caused by helicobacter pylori In 2013 Chinese and Israeli scientists reported a successful pilot study of a Breathalyzer-style breath test intended to diagnose stomach cancer by analyzing exhaled chemicals without the need for an intrusive endoscopy,in necks of the glands; near openings of gastric pitsChief CellsWhat do they secrete?secretes pepsinogen- the inactive enzyme precursor to pepsinWhere are they located?in the deeper parts of the gastric glandsParietal CellsWhat do they secrete?in the middle of the gastric glandsWhere are they located?Hydrochloric acid; aids in the activation of pepsinogen

Intrinsic factor; helps the small intestine absorb B12pain is caused by holes in the mucosal lining of the esophagus due to regurgitation of stomach acidsymptoms include heartburn, pain with swallowing, increased salivation, nausea, chest pain and coughingfactors that may contribute to acid reflux include obesity, gall stones, hernias, viceroptis products of these cells together form Gastric JuiceGastric Glands: glands in the stomach wall that secrete gastric juice1. Chief cells in the stomach wall secrete pepsinogen and parietal cells secrete hydrochloric acid2. when these two secretions mix, the HCl breaks down pepsinogen, forming the enzyme pepsin3. pepsin begins chemical digestion in the stomach by splitting proteins and digesting them into polypeptides